JPH04172999A - Driving circuit for stepping motor - Google Patents

Abstract

PURPOSE:To eliminate noise to be generated at a power source line by simultaneously turning two transistors of a ground side for forming an H bridge to ON at the time of stopping a motor. CONSTITUTION:The output of a driving circuit 8 at the time of stopping a motor is varied from a low level to an M level at this time, and two Q3, Q4 of four transistors Q1 to Q4 for constituting an H bridge are turned ON by the operation of a changeover switch circuit 6 composed of diodes D5, D6, D7. If the circuit 8 is not formed at the time of stopping the motor, counterelectromotive force of a motor coil 9 regenerated in a motor driving power source Vm 11 through the diode D1 or D2 at the moment of stopping the motor is discharged through a loop of the transistor Q3 and the diode D4 or the transistor Q4 and the diode D3, and hence influence to the power source 11 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stepping motor drive circuit, and more particularly to a drive circuit that reduces noise on a power supply line when a drive transistor is off.

[Conventional technology]

In a conventional stepping motor drive circuit for a bipolar motor, the output stage transistors are arranged in an H-type configuration and are alternately turned on and off to control the rotation of the stepping motor.

On the other hand, when the motor is stopped, all four transistors forming the H-bridge are turned off.

[Problem to be solved by the invention]

The conventional stepping motor drive circuit described above has a structure in which all transistors 8 are turned off when the motor stops, so the moment the stepping motor shifts from the rotating state to the stopped state, the inductance (L) load component of the two motors causes a reverse effect. Since an electromotive voltage is generated and instantaneously regenerated on the power line, there is a drawback that noise is generated on the power line.

SUMMARY OF THE INVENTION An object of the present invention is to provide a stepping motor drive circuit that solves the above-mentioned drawbacks and prevents noise from occurring in the power supply line.

[Means to solve the problem]

The configuration of the stepping motor drive circuit of the present invention is such that in a stepping motor drive circuit that drives a step-sobbing motor with an H bridge, when the motor is stopped, two ground-side transistors forming the H bridge are turned on at the same time. It is characterized by

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing a stepping motor drive circuit according to an embodiment of the present invention. FIG. 2 shows one of two H-bridge drive circuits.

In FIG. 1, the drive circuit of this embodiment has an H bridge 3
, drive buffer 4.5, and diodes D6, D7 . D
Each changeover switch circuit consists of 5 6.6', 6"
, a motor stop drive circuit 88 consisting of an inverter, an excitation switching circuit 7, and level shifters 2o and 2o'. The excitation switching circuit 7 is a two-man power AND gate 2.
and an inverter, and the drive bus sofa 4 has a transistor Q5. Q6 in series, and the drive buffer 5 has similar transistors Q7 . The H-bridge 3 has transistors Q1, Q2 . Q3.04 and diode D1. D2゜D3. D4 are connected in a bridge manner and connected to the motor coil 9.

In this embodiment, N-channel power MO3FETs are used as the driving transistors Q1 to Q4 constituting the H bridge 3, and transistors Q1. Transistor Q5 for driving Q4. The drive buffer 4 composed of transistors Q6 is connected to transistors Q2. Transistor Q7 for driving Q3. Q8
A drive buffer 5 consisting of the following is used. stop signal 2
is at a high level when the stepping motor is rotating, and depending on the level of excitation switching signal 1, in excitation switching circuit 7,
The on state of the output transistor is determined. Specifically, when excitation signal 1 is at a high level, transistor Q1. Q
When transistor Q2.4 is turned on and at a low level, transistor Q2. QB
turns on. As a result, the driving current direction of the motor coil 9 is controlled, and the rotation operation of the step-I ping motor is performed.

In this state, the output level of the drive circuit N8 when the motor is stopped is at a low level, and the influence on other circuits is cut off by the diode D7 that constitutes the changeover switch circuit 6.

This embodiment differs from the conventional stepping motor drive circuit described above in that when the stepping motor is stopped, two of the four transistors forming the H bridge on the GND side are turned on simultaneously.

Now, when the stop signal 2 changes from high level to low level, the output of the excitation switching circuit 7 becomes low level, and the output of the transistor Q1. Q4 drive buffer 4, transistor Q2
．． The output of the QB drive buffer 5 also becomes low level, and the drive from the gate drive power supply v610 is cut off.

On the other hand, the output of the motor stop drive circuit 8 changes from the low level to the M level at this time, and the output of the drive circuit 8 changes from the low level to the M level.
．． D6. Due to the function of the changeover switch circuit 6 constituted by D7, the two GND side transistors Q3 .
04 is turned on.

As a result of this operation, when there is no drive circuit 8 when the motor is stopped, the back electromotive voltage of the motor coil 9, which was regenerated to the motor drive power supply V, 11 through the diode D1 or the diode D2 at the moment when the motor stopped, is transferred to the transistor Q.
3 and the diode D4, or through the loop of the transistor Q4 and the diode D3, the influence on the motor drive power source 11 can be reduced.

The stepping motor drive circuit according to this embodiment includes, in addition to a normal drive circuit, a changeover switch using a diode and a drive circuit when the motor is stopped.

FIG. 2 is a circuit diagram showing part of a drive circuit according to another embodiment of the present invention. In FIG. 2, this embodiment replaces the transistor Q3 in FIG. 1 with four transistors Q31 .
Q32. Q33. It consists of Q34. The other parts are the same as in FIG.

In this embodiment, four transistors Q31°QB2 . Q
33. Q34 is connected in parallel, a diode D5 is connected to the gates of transistor Q31 and transistor Q34, and further connected to diode D7, and transistor Q
The gate of transistor Q7. Connected to the gate of Q8.

In this embodiment, transistors Q31 to Q3 with the same on-resistance
4, and the changeover switch circuit 6 is used only for the transistor Q31.In this case, the on-resistance of the transistor on the lower side of the H bridge can be compared during rotation, and it can be increased four times during regeneration. If you use various methods,
Fine adjustment of regeneration time is also possible.

〔Effect of the invention〕

As explained above, the present invention provides a GN to
By simultaneously turning on the two transistors D(!!I), the regeneration operation of the back electromotive voltage of the motor coil can be performed without feeding back to the motor drive power supply, which has the effect of reducing noise on the power supply line.

Furthermore, the present invention has the advantage that by changing the on-resistance of the transistor during rotational operation and during regeneration, it is possible to perform an optimal regenerative operation in accordance with the motor characteristics and load characteristics.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a stepping motor drive circuit according to one embodiment of the present invention, and FIG. 2 is a circuit diagram showing a portion of another embodiment of the present invention. 1... Excitation switching signal, 2... Stop signal, 3... H
Bridge, 4-...Ql, Q4 drive buffer, 5...
・Q2゜Q3 drive buffer, 6... Changeover switch circuit, 7... Excitation switching circuit, 8... Motor stop drive circuit, 9... Motor coil, 10 - Gate drive power supply, 1]...・Motor drive power supply.

Claims (1)

[Claims] In a stepping motor drive circuit that drives a stepping motor with an H bridge, when the motor is stopped,
A stepping motor drive circuit characterized in that two ground-side transistors constituting the H-bridge are turned on at the same time.